LAUSR

In the 5th generation (5G) unlicensed band communication, listen-before-talk (LBT) is a key mechanism to allow fair coexistence with other radio access technologies (RATs). With LBT, the user device (UE) needs to transmit a reservation signal (RS) between LBT success and the next slot boundary to avoid competing transmission from other RATs. This scheme, on the other hand, also blocks other UEs from accessing to the base station (BS). The uplink multiple access ability is prominently degraded due to LBT. In this article, an improved LBT scheme is proposed for uplink transmission in the 5G unlicensed band. The RS is enhanced by carrying an indicator of a successful LBT. Other UEs of the same RAT check for enhanced RS in addition to the conventional energy detection. Once the enhanced RS is detected, UE stops LBT, mutes until the next slot boundary, and transmits data in the next slot. We provide theoretical performance analysis of the proposed scheme. Comparisons are carried out between the proposed scheme and other existing schemes. The proposed scheme has better performance than other schemes. In a typical uplink transmission scenario, the proposed scheme improves the average number of UEs with successful LBT by 92% over the existing scheme. In addition, the proposed scheme can be easily deployed complying with the current LBT framework of the 5G unlicensed band.